This invention relates in general to detection devices and in more particular to a system for detecting the condition of spark gap ignition assemblies.
Industrial and commercial oil burners and gas burners typically employ a fuel pilot assembly, where the fuel is usually gas or oil. The fuel pilot is ignited by means of an arc generated by a high voltage across an ignition spark gap in a spark gap ignition assembly. The arc ignites a fuel mixture supplied to the vicinity of the gap, thus starting the fuel pilot.
The conditions of the spark gap ignition assembly may change due to continuous use. Thus a carbon hair (frequently caused by too much fuel in the fuel-air mixture) may build up bridging the spark gap, thereby shorting out the gap. Malfunctions may cause the pressure of the air and fuel mixture to be too high or too low, thereby affecting the stability of the arc for the fuel pilot to be started properly. Wear and tear on the spark gap assembly may also affect the proper lighting of the fuel pilot. Thus the transformer may supply no or too low a voltage for starting an arc. The wires connecting the transformer to the spark gap may become worn and shorted out so that no or too low a voltage appears across the gap and no arc can be started.
The spark gap ignition assembly is usually located deep inside the industrial or commercial burner. While the above described malfunctions can be discovered by disassembling the spark gap assembly, such procedure is tedious and time consuming and would require lengthy shutdown of the burner. It is therefore desirable to provide an instrument by which the above described malfunctions can be detected without disassembling the spark gap assembly and without shutting down the burner.
Control systems for industrial or commercial burners have been increasingly automated. Frequently the burners are controlled by an elaborate control system, complete with sophisticated detection equipment and computer control system which monitor every facet of the burners, except for directly monitoring the spark gap ignition assembly. The control system for industrial or commercial burners usually includes an infrared (IR) or ultraviolet (UV) detector or both for sensing whether the fuel pilot flame is on. When the detectors detect the presence of the pilot flame, the control system then causes the main fuel valve to be turned on for lighting the main burner.
One of the most frequent causes of burner malfunction is a defective spark gap ignition assembly. Most control systems for burners, however, do not include any dedicated device for testing the condition of the spark gap ignition assembly apart from the IR or UV detectors. The failure of the fuel pilot flame to be lit can be caused by a number of factors, including a defective fuel valve, malfunctions of the control system or a defective spark gap ignition assembly. The IR or UV detector, however, detects only whether the fuel pilot is on but cannot identify the cause of the failure. Thus if the fuel pilot flame fails to light, a user would frequently diagnose and correct the problem by trial and error. Thus one frequent cause of the failure is the build up of a carbon hair bridging the spark gap. A user may simply change the control system at a cost of about $500 to $2500. Air blowing across the spark gap during a pre-purge or post-purge cycle, the vibration of the burner and/or the change of the control system may cause the carbon hair to fall off. Hence while changing the control system may have temporarily solved the problem, the carbon will build up again causing another failure of the fuel pilot. Thus without a separate device for detecting the condition of the spark gap ignition assembly as proposed by applicant herein, the process of identifying the cause of pilot flame failure can tax the patience of a user.
A conventional instrument used in conjunction with control systems for burners is the Katy Spark Ignition Controls Tester, available from James Kamm Tech, P.O. Box 47673, Toledo, Ohio 43624. The Katy Spark Ignition Controls Tester is essentially a meter having AC and DC volt ranges with electrical leads. The leads are connected to external test jacks in the control system to receive signals originating from the IR or UV detectors to indicate the presence or absence of the fuel pilot flame. Thus while the Katy Tester does give the user an indication of whether the fuel pilot flame is lit or not which many control systems do not. However, the Katy Tester still cannot identify whether the failure of the fuel pilot is caused by a defective fuel valve, a defective spark gap ignition or still other causes.
None of the above described systems is satisfactory. It is therefore desirable to provide an improved system for testing the various malfunctions of the ignition assembly, without shutting down the burner and without retrieving or disassembling the spark gap ignition assembly.